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#459529 - 10/12/18 07:21 AM MAJOR tech question - PA900
Uncle Dave Offline
Senior Member

Registered: 12/01/99
Posts: 12800
Loc: Penn Yan, NY
I doubt that any real kb techs monitor this forum, but here goes:

I changed the key contacts in my PA900, and after reassembling it, putting in the MANY, many screws, and figuring out how to make sure the keys don't bounce (there's a very specific way to reinsert the circuit board after you deal with the contacts), I powered it up to find ... a very strange anomaly. The bottom 2/3 of the keys function as they should, but starting at the top and going down, every 4th key will not sound. It's a cyclical pattern that repeats for more than an octave.
Can anyone think of a mechanical reason why this would occur? The contact strips come in lengths of 12 (and one of 13), so that kind of rules out any one strip as a target for my attention. The 1 in 4 dead key issue is a real brain tease.

I updated the OS, reinstalled the resources, and did everything I could think of to overcome a software issue. I have a sneaky suspicion that there's a loose wire, or ribbon, or "something" that I didn't connect correctly ... although I was pretty thorough as I unplugged and re plugged those things.

I'm baffled, and open to educated suggestions.
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#459533 - 10/12/18 08:51 AM Re: MAJOR tech question - PA900 [Re: Uncle Dave]
Dnj Offline
Senior Member

Registered: 09/21/00
Posts: 43703
Dave can you call Korg service and see what they think?

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#459534 - 10/12/18 09:02 AM Re: MAJOR tech question - PA900 [Re: Uncle Dave]
DonM Offline
Senior Member

Registered: 06/25/99
Posts: 16735
Loc: Benton, LA, USA
Best to try to get help on the Korg Forums. Probably PA4 Forum has the most readers.
http://www.korgforums.com/forum/phpBB2/viewforum.php?f=76
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#459545 - 10/12/18 10:58 AM Re: MAJOR tech question - PA900 [Re: DonM]
Uncle Dave Offline
Senior Member

Registered: 12/01/99
Posts: 12800
Loc: Penn Yan, NY
After talking with Fran, I ruled out a motherboard issue. The sounds and features all work, EXCEPT those few keys I mentioned. This is most likely a short, or crack in the circuit board. MIDI works as it should, as do the recorder, players, rhythms and sounds. "SOMETHING" in the keybed, or connections has failed.

I retired the unit to sit atop my Rhodes and serve as a sound source, a monitor amp/speakers, a quick MP3 recorder, and general cool stack topper.

How's it look?
(The kb stuffed in the middle is a Korg i5s that I got from Boo. It serves as a controller for the 900, so I don't have to reach) I play bass lines, and accent sounds on that, while I comp on the Rhodes. Like the old days smile


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Edited by Uncle Dave (10/12/18 11:00 AM)
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#459551 - 10/12/18 11:53 AM Re: MAJOR tech question - PA900 [Re: Uncle Dave]
solomon8 Offline
Member

Registered: 12/20/05
Posts: 98
Loc: Lehigh Acres, Fl USA
Did you try disconnecting the connector cable and reconnecting it. I would try that. Can't hurt. It sounds like a connection problem. Are you sure you connected all the connectors. Not criticizing your skills, just sometimes it is easy to miss a cable when taking things apart. Best of luck to you.

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#459552 - 10/12/18 12:15 PM Re: MAJOR tech question - PA900 [Re: Uncle Dave]
Uncle Dave Offline
Senior Member

Registered: 12/01/99
Posts: 12800
Loc: Penn Yan, NY
As far as I know, and I was very careful to count ... I connected all cables that I disconnected. I did this whole thing 3 times ... same result. My best guess is a damaged circuit board. maybe I screwed it in too tight, maybe a flash of static electricity found it's way in ...who knows? As for now - I'm happy where it is. Someday I may open it up again, but it serves a purpose as it is. Sooooooo many screws. Who's got that kinda time?
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#459556 - 10/12/18 01:01 PM Re: MAJOR tech question - PA900 [Re: Uncle Dave]
cgiles Offline
Senior Member

Registered: 09/29/05
Posts: 6703
Loc: Roswell,GA/USA
In addition to cable connectors, there is one other vulnerability that we often overlook. I had an intermittent problem with my organ (KeyB) that was driving me crazy. Description of the problem is unimportant but it was obviously electronic. I described the problem over on the Keyboard Corners forum and someone suggested that I RESEAT the 4 main circuit boards (one for each set of drawbars). Despite a lot of skepticism on my part, I tried it. Three of the four could be seated more firmly into the motherboard. After reseating and closing up, I turned it on and Voila!, no more problems. That was two years ago and I have not had even a hint of a problem since (and I play it daily - extensively). Yeah, yeah, I know....the screws, but it might be worth a try.

chas
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#459557 - 10/12/18 01:06 PM Re: MAJOR tech question - PA900 [Re: cgiles]
Uncle Dave Offline
Senior Member

Registered: 12/01/99
Posts: 12800
Loc: Penn Yan, NY
Originally Posted By cgiles
RESEAT the 4 main circuit boards


The circuit board that controls the keys is a two piece design that's held together with aluminum type tape, or something like it. It's VERY possible that it's not seated perfectly. With the multiple connect - disconnect dance I performed, it's very likely that the board has been put back in a slightly "off" position. Good thinking. Not excited to take it apart again anytime soon, but .... maybe someday. Thanks!
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